Comparative study of perovskites as cathode contact materials between an La0.8Sr0.2FeO3 cathode and a Crofer22APU interconnect in solid oxide fuel cells

Perovskites of different compositions were tested as cathode contact material between an La0.8Sr0.2FeO3 cathode and a Crofer22APU interconnect by resistance measurements at 800 °C. The materials tested were LaNi0.6Fe0.4O3 and La0.8Sr0.2FeO3 which are also used as cathodes; La0.8Sr0.2Mn0.5Co0.5O3 and La0.8Sr0.2Mn0.1Co0.3Fe0.6O3, selected for comparing perovskites with different Mn contents; and La0.8Sr0.2Co0.75Fe0.25O3 and La0.8Sr0.2Co0.75Cu0.25O3 for comparing perovskites with high Co content and two possible partial substitutions of the Co. The initial area-specific contact resistance (ASR) was found to depend on the electrical conductivity of the measured perovskites. Time evolution of the ASR depended on the interactions between the contact material and the interconnect, showing the highest degradation rates for LaNi0.6Fe0.4O3 and La0.8Sr0.2FeO3. Chromium from the interconnect reacted with the Sr-containing perovskites forming SrCrO4. With the contact material without strontium chromium-containing perovskites were formed. A reduced interfacial reaction was achieved by application of a MnCo1.9Fe0.1O4 spinel protection layer on Crofer22APU in terms resulting in low and stable ASR.